| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.3 052/157] ALSA: seq: Fix race at timer setup and close | Date | Wed, 27 Jan 2016 10:11:59 -0800 |
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4.3-stable review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai <tiwai@suse.de>
commit 3567eb6af614dac436c4b16a8d426f9faed639b3 upstream.
ALSA sequencer code has an open race between the timer setup ioctl and the close of the client. This was triggered by syzkaller fuzzer, and a use-after-free was caught there as a result.
This patch papers over it by adding a proper queue->timer_mutex lock around the timer-related calls in the relevant code path.
Reported-by: Dmitry Vyukov <dvyukov@google.com> Tested-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- sound/core/seq/seq_queue.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/sound/core/seq/seq_queue.c +++ b/sound/core/seq/seq_queue.c @@ -142,8 +142,10 @@ static struct snd_seq_queue *queue_new(i static void queue_delete(struct snd_seq_queue *q) { /* stop and release the timer */ + mutex_lock(&q->timer_mutex); snd_seq_timer_stop(q->timer); snd_seq_timer_close(q); + mutex_unlock(&q->timer_mutex); /* wait until access free */ snd_use_lock_sync(&q->use_lock); /* release resources... */
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